Phosphorus reserves increase grass regrowth after defoliation

MARIANO OYARZABAL; MARTÍN OESTERHELD

OECOLOGIA

SPRINGER

Año: 2009 p. 717 - 724

0029-8549

Abstract Accumulation of P above levels that promotegrowth, a common plant response called “luxury consumption”,can be considered as a form of reserve to supportfuture growth when the nutrient can subsequently be mobilized.However, the eVect of P reserves on regrowth followingdefoliation has not been demonstrated. We tested thehypothesis that P luxury consumption increases plant toleranceto defoliation. We performed two experiments withfour grass species from a continuously grazed temperategrassland in the Flooding Pampa (Argentina). The Wrstexperiment, aimed at generating P luxury consumption byfertilization, resulted in one species (Sporobolus indicus)showing luxury consumption. In this way, we were able toobtain plants of S. indicus with similar biomass but contrastingamounts of P reserves. The second experimentevaluated the subsequent regrowth following defoliation ona P-free medium of these plants diVering in P reserves.Regrowth was larger for plants that had shown P luxuryconsumption during a previous period than for plants withlower levels of P reserves. During regrowth these plantsshowed a clear pattern of P remobilization from the stubble,crown, and root compartments to the regrowing tissue, inaddition to a likely reutilization of P present in leaf-growthzones. This work is the Wrst showing that high levels of Preserves can confer tolerance to defoliation by promotingcompensatory growth under P deWciency.